A firefight between NATO troops and their Afghan allies killed five people in circumstances that remained murky Sunday against a background of increasing 'insider' attacks on coalition troops.
A NATO soldier, a civilian contractor and three Afghan troops died in an exchange of fire Saturday evening in Wardak province west of the capital Kabul, the International Security Assistance Force said.
"What was initially reported to have been a suspected insider attack is now understood to possibly have involved insurgent fire," deputy ISAF commander Lt. Gen. Adrian Bradshaw told a hastily-called press conference.
"The incident occurred while an ISAF unit was manning a temporary check point in an area near an Afghan National Army unit.
"According to ISAF and ANA reporting, after a short conversation took place between ANA and ISAF personnel, firing occurred which resulted in the fatal wounding of an ISAF soldier and the death of his civilian colleague.
"In an ensuing exchange of fire three ANA personnel are reported to have died."
Bradshaw said the incident was still under investigation, adding: "The circumstances were somewhat confused and we are establishing the full facts."
Provincial police spokesman Abdul Wali told AFP that the shooting broke out after "a verbal dispute" between the two sides.
Ministry of Defence deputy spokesman General Daulat Waziri said the incident was a result of a "misunderstanding", adding that it was investigating whether insurgent fire was involved.
Three ANA soldiers were killed and three wounded, he said.
The shootout comes amidst heightened tensions between NATO troops and their Afghan allies in the wake of spiralling "green-on-blue" attacks in which Afghan security forces turn their weapons on their Western allies.
At least 51 coalition troops have been killed in such assaults this year - about 15 per cent of all NATO deaths - and the top ISAF general has described them as the signature attack' of the Afghan war.